1. Field of the Invention
The present invention relates to an apparatus for detecting the wheel positions of a vehicle, on which respective wheels are installed, and an apparatus for detecting the inflation pressure of the tires of a vehicle, such as a direct-type tire inflation pressure detection apparatus.
2. Description of the Related Art
A direct-type apparatus for detecting the inflation pressure of tires of a vehicle is known. This tire inflation pressure detecting apparatus is provided with a transceiver equipped with a sensor such as a pressure sensor, which is directly installed on each wheel with a tire. An antenna and a receiver are provided in the vehicle body. Thus, when the receiver receives, via the antenna, from the transmitter a detection signal detected by the sensor, the receiver is able to detect the inflation pressure of each tire based on the received detection signal.
In this direct-type tire inflation pressure detecting apparatus, it is determined whether or not data which has been received is coming from the transceiver of the own vehicle and it is determined on which of the wheels a transceiver in question is installed. For these determinations, as shown in U.S. Pat. No. 5,602,524 (which corresponds to Japanese Patent No. 3212311), data to be transmitted from each transceiver additionally contains ID (identification) information to distinguish the own vehicle from other vehicles and identify each wheel with the transceiver. The ID information is previously stored in the receiver and, when the receiver receives data from the transceiver, the stored ID information and the received ID information are used to determine the wheel the data is coming from.
However, the foregoing conventional detecting apparatus is confronted with a difficulty. Specifically, the determination of the respective wheels equipped with the respective transceivers requires that inherent ID information be contained in data transmitted from each transceiver. Hence, if the ID information is not used, it is impossible to distinguish data coming from each transceiver from data coming from other transceivers. That is, the positions of the respective wheels cannot be detected without using the ID information.
The foregoing conventional detecting apparatus is confronted with another difficulty. Specifically, when a user changes the positions of the tires by rotation, for example, the user has to read the ID information of the rotated tires and renew the ID information that has been registered up to then. Without doing this, the tire inflation pressure detecting apparatus cannot cope with the position change of the wheels.
Therefore, it is desired that a tire inflation pressure detecting apparatus can detect the wheels equipped with the respective transceivers without using the ID information (wheel-position information). In other words, it is desired that a tire inflation pressure detecting apparatus can detect the positions on which the respective transceivers are installed. Alternatively, where it is necessary to renew the ID information because of the position change of the wheels, the renewal of the ID data is desired to be automatically performed.